Method of injection molding opening devices on sheet material for packaging pourable food products, and packaging material and package obtained thereby

ABSTRACT

A method of injection molding an opening device on sheet packaging material for packaging pourable food products; the packaging material has at least a first and a second layer, and an opening formed through the first layer and sealed by a cover portion of the second layer; the method includes the steps of injecting molten plastic material onto a first side of the cover portion of the second layer, feeding the molten plastic material along the cover portion to cover it on the first side, and feeding the molten plastic material through an annular peripheral portion of the cover portion to form a spout of the opening device projecting from a second side, opposite the first side, of the cover portion; the molten plastic material covers the cover portion to define, with the cover portion, a user-removable sealing portion of the spout.

This application is a divisional of U.S. application Ser. No. 12/663,069having a filing date of Dec. 4, 2009 which is a U.S. national stageapplication based on International Application No. PCT/EP2008/058334having a filing date of Jun. 27, 2008, and claims priority to EuropeanApplication No. 07425401.2 having a filing date of Jun. 28, 2007, theentire content of all three of which is incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a method of injection molding openingdevices on sheet material for packaging pourable food products, and tothe packaging material and package obtained using such a method.

BACKGROUND ART

As is known, many pourable food products, such as fruit juice, UHT(ultra-high-temperature treated) milk, wine, tomato sauce, etc., aresold in packages made of sterilized packaging material.

A typical example of this type of package is the parallelepiped-shapedpackage for liquid or pourable food products known as TETRA BRIK Aseptic(registered trademark), which is made by folding and sealing laminatedstrip packaging material.

The packaging material has a multilayer structure substantiallycomprising a base layer for stiffness and strength, which may comprise alayer of fibrous material, e.g. paper, or mineral-filled polypropylenematerial; and a number of lamination layers of heat-seal plasticmaterial, e.g. polyethylene films, covering both sides of the baselayer.

In the case of aseptic packages for long-storage products, such as UHTmilk, the packaging material also comprises a layer of gas-barriermaterial, e.g. aluminium foil or ethyl vinyl alcohol (EVOH) film, whichis superimposed on a layer of heat-seal plastic material, and is in turncovered with another layer of heat-seal plastic material forming theinner face of the package eventually contacting the food product.

Packages of this sort are normally produced on fully automatic packagingmachines, on which a continuous tube is formed from the web-fedpackaging material; the web of packaging material is sterilized on thepackaging machine, e.g. by applying a chemical sterilizing agent, suchas a hydrogen peroxide solution, which, once sterilization is completed,is removed from the surfaces of the packaging material, e.g. evaporatedby heating; and the web of packaging material so sterilized ismaintained in a closed, sterile environment, and is folded and sealedlongitudinally to form a vertical tube.

The tube is filled with the sterilized or sterile-processed foodproduct, and is sealed and subsequently cut along equally spaced crosssections to form pillow packs, which are then folded mechanically toform respective finished, e.g. substantially parallelepiped-shaped,packages.

Alternatively, the packaging material may be cut into blanks, which areformed into packages on forming spindles, and the packages are filledwith the food product and sealed. One example of this type of package isthe so-called “gable-top” package known by the trade name TETRA REX(registered trademark).

To open the packages described above, various solutions have beenproposed, including reclosable opening devices made of plastic materialand substantially comprising a spout, e.g. tubular, defining a throughopening and fitted to a hole in a wall of the package; and a removable,e.g. screw or hinged, cap fitted to and outwardly closing the spout.

When producing the opening device, the opening of the spout is sealed bya plastic membrane connected integrally to the spout and detachable fromit along a normally circular tear line; and, on the side facing the cap,the membrane has an integral projecting pull ring, the free end of whichis pulled by the user to detach the membrane from the spout along thetear line and so open the product pour opening. More specifically, thepull ring extends inside, and at a predetermined distance from, thespout.

Using the opening devices described, the package is easy to open, with areasonable amount of twist required of the user, and the membrane isdetached neatly from the spout.

The same does not apply, however, in the case of packages requiring notonly liquid but also gas sealing where the opening device is fitted tothe packaging material.

In such cases, solutions are known in which the membrane of the openingdevice is fixed directly over a prelaminated hole in the packagingmaterial, i.e. a hole formed in the base layer only and covered by theother lamination layers, including the layer of gas-barrier material.

Using this solution, opening the package calls not only for detachingthe membrane from the spout, but also for tearing the layer of barriermaterial against the edge of the hole through the base layer. Withcommonly used barrier materials, such as aluminium, this invariablyresults in a jagged, frayed edge of the hole, thus impairing smoothpour-out of the food product.

DISCLOSURE OF INVENTION

One object of the present invention is to provide an injection moldingmethod by which to apply plastic opening devices cheaply and easily tosheet packaging materials to obtain sealed packages of pourable foodproducts of improved opening and pour characteristics as compared withthe aforementioned known packages.

Another object of the present invention is to provide an injectionmolding method by which to apply plastic opening devices cheaply andeasily to sheet packaging materials to obtain sealed packages ofpourable food products capable of ensuring effective gas sealing.

At least one of the above objects is achieved by the present invention,which relates to a method of injection molding an opening device on asheet packaging material for packaging pourable food products.

The present invention also relates to a sheet material for packagingpourable food products.

The present invention also relates to a sealed package for packagingpourable food products.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred, non-limiting embodiment of the present invention will bedescribed by way of example with reference to the accompanying drawings,in which:

FIG. 1 shows a partly sectioned, exploded side view of a sealed packagefor pourable food products, made of sheet material on which an openingdevice is injection molded using the method according to the presentinvention;

FIG. 2 shows a section of the FIG. 1 sheet material before the openingdevice is applied;

FIGS. 3 to 7 show sections of the FIG. 2 sheet material at successivesteps in injection molding the opening device.

BEST MODE FOR CARRYING OUT THE INVENTION

Number 1 in FIG. 1 indicates as a whole a sealed package for pourablefood products, made of a multilayer sheet material 2 which is folded andsealed in known manner as described in detail above, and to which anopening device 3 of plastic material is applied using the injectionmolding method according to the present invention.

In the example shown, package 1 is parallelepiped-shaped and of the typeknown by the trade name TETRA BRIK Aseptic (registered trademark). Themethod according to the present invention, however, also applies toadvantage to other types of packages, such as the gable-top packagesknown by the trade name TETRA REX (registered trademark).

With particular reference to FIG. 2, material 2 comprises a base layer 4for stiffness and strength, which may be made of fibrous material, e.g.paper, or mineral-filled polypropylene material; and a number of layers5, 7 of heat-seal plastic material, e.g. polyethylene films, coveringboth sides of base layer 4.

In the case of an aseptic package 1 for long-storage products, such asUHT milk, packaging material 2 also comprises a layer 6 of gas-barriermaterial, e.g. aluminium foil or ethyl vinyl alcohol (EVOH) film, whichis superimposed on a layer 7 of heat-seal plastic material, and is inturn covered with another layer 5 of heat-seal plastic material formingthe inner face of package 1 eventually contacting the food product.

In other words, layers 5, 6 and 7 define respective lamination layersapplied to base layer 4 when producing material 2 in the form of acontinuous strip.

Strip material 2 also comprises a number of removable portions 8 (onlyone shown in the drawings) equally spaced in a lengthwise direction A ofthe material, and to which opening devices 3 are subsequently injectionmolded.

In the following description, reference is made to one removable portion8 and one opening device 3 for the sake of simplicity.

In the example shown, removable portion 8 is defined by a so-calledprelaminated hole, i.e. a hole (or opening) 9 formed through base layer4 of material 2 and covered by lamination layers 5, 6, 7, so that hole 9is sealed by a respective sheet cover portion 10.

In an alternative embodiment not shown, cover portion 10 may even bedefined by only one or some of layers 5, 6, 7. For example, coverportion 10 may be made solely of gas-barrier material.

In another alternative embodiment not shown, cover portion 10 may bedefined by a patch fixed to the rest of material 2 to seal a holeformed, in this case, through the full thickness of material 2.

As shown in particular in FIG. 1, opening device 3 has an axis Bperpendicular to the lengthwise direction A of strip material 2, andsubstantially comprises a membrane attachment portion 11 adhering to oneside 10 a of cover portion 10—in the example shown, the side eventuallyfacing inwards of package 1; and a cylindrical tubular spout 12, whichis fixed to material 2, about hole 9, defines an opening 16 by which topour the food product from package 1, and extends through cover portion10 so as to extend on both sides 10 a, 10 b of the cover portion.Opening device 3 also comprises a cap 13 (FIG. 1) which fits removablyto spout 12 to outwardly close opening 16.

More specifically, attachment portion 11 and spout 12 are injectionmolded in one piece; and cap 13 is formed separately from the wholecomprising attachment portion 11 and spout 12.

Attachment portion 11 and cover portion 10 of hole 9 together define asealing portion 15 sealing opening 16 of spout 12.

As shown particularly in FIG. 1, spout 12 comprises an annular flangeportion 17 fixed to material 2, about hole 9; and a cylindrical tubularneck portion 18 projecting axially from an inner lateral edge of flangeportion 17, and extending through a peripheral annular portion of coverportion 10. In other words, neck portion 18 projects from material 2 onside 10 b opposite the side (10 a) to which attachment portion 11 isfixed.

As shown in FIG. 1, attachment portion 11 and flange portion 17 arejoined by an annular portion 19, which is smaller in section thanportions 11 and 17, so as to tear easily to detach sealing portion 15from spout 12. In other words, annular portion 19 defines a tear linealong which to detach attachment portion 11 from spout 12.

On the side facing cap 13, attachment portion 11 has an integralprojecting pull ring 21, by which to detach sealing portion 15 fromspout 12 along annular portion 19 and so open opening 16 to pour out theproduct.

More specifically, pull ring 21 extends inside, and at a predetermineddistance from, neck portion 18, and is joined to attachment portion 11by a tab 22.

As shown in FIG. 1, cap 13 is a screw type, and has a cylindricallateral wall 23 with an inner thread 24, which engages a correspondingouter thread 25 on neck portion 18 of spout 12.

The method of injection molding opening device 3 on material 2 is asfollows.

Strip material 2, in the FIG. 2 configuration, is step-fed in directionA to position a removable portion 8 inside a known molding unit 30(FIGS. 3 to 7) only illustrated as necessary for a clear understandingof the method according to the present invention.

With reference to FIGS. 3 to 7, molding unit 30 comprises a number ofmolds 30 a, 30 b, 30 c, 30 d, which are coaxial with axis B of theopening device 3 being formed, are located on both sides of material 2,and are movable between an open configuration (not shown) allowing feedof material 2 in direction A, and a closed configuration (FIGS. 3 to 7),in which they define a closed mold cavity 31 which is filled with moltenplastic material to define, when the material sets, the whole comprisingattachment portion 11 and spout 12.

In the example shown, molds 30 b, 30 c, 30 d are located on the oppositeside of material 2 to mold 30 a; and, as shown in FIGS. 3 to 7, mold 30c is interposed radially between molds 30 b and 30 d.

Mold cavity 31 comprises a substantially disk-shaped first portion 32 ofaxis B; a cylindrical tubular second portion 33 extending, coaxiallywith axis B, from one side of a flat peripheral annular portion 34 ofportion 32; and a third portion 35 which defines pull ring 21 ofattachment portion 11, and extends from the same side as portion 33, andfrom a radially inner point of portion 32 with respect to peripheralannular portion 34.

Portion 32 comprises a convex central portion 36 curving towardsportions 33 and 35, and which is connected to peripheral annular portion34, and is connected, at axis B, to a molten plastic injection conduit37.

In the FIG. 3-7 example, portion 32 is defined by mold 30 a on one side,and by molds 30 b, 30 c, 30 d on the opposite side; portion 33 isdefined by molds 30 c and 30 b; portion 35 is defined by molds 30 c and30 d; and conduit 37 extends through mold 30 a.

As explained in detail below, portion 32 defines attachment portion 11and flange portion 17 of spout 12, and portion 33 defines neck portion18 of spout 12.

To mold opening device 3, material 2 is stopped inside molding unit 30in the FIG. 3 configuration, in which cover portion 10 is housedcompletely, and totally undamaged, inside disk-shaped portion 32 of moldcavity 31. More specifically, cover portion 10 is positioned with side10 b facing portions 33 and 35 of mold cavity 31.

At this point, from side 10 a of cover portion 10, molten plasticmaterial is injected along conduit 37 into portion 32 of mold cavity 31,which is gradually filled from central portion 36 towards peripheralannular portion 34.

The pressure of the molten plastic material injected into portion 32 ofmold cavity 31 pushes cover portion 10 of material 2 against mold 30 d,so that side 10 b of cover portion 10 contacts mold 30 d.

At this stage, layer 5 of heat-seal plastic material of cover portion10, facing mold 30 a, melts completely with the plastic materialinjected into mold cavity 31.

The molten plastic material spreads radially inside portion 32 until iteventually reaches the intersection of portions 32 and 35, where coverportion 10, having no solid support by molds 30 d and 30 c, is piercedneatly by the pressure of the molten plastic material, which thereforefills the whole of portion 35 to form pull ring 21.

In exactly the same way, when the molten plastic material reaches theannular portion at the intersection of portions 32 and 33, cover portion10 is pierced neatly by the pressure of the molten plastic material,which therefore flows into portion 33 to form neck portion 18 of spout12 and thread 25.

In other words, the molten plastic material pierces through coverportion 10 at the intersections between portion 32 and portions 33 and35 of mold cavity 31 to form through openings, which are subsequentlysealed off by the plastic material to fully restore the integrity ofmaterial 2.

As specifically shown in FIGS. 6 and 7, because of the particular shapeof the annular zone at the intersection of portions 32 and 33, and thehigh speed of the molten plastic material at that portion, cover portion10 is removed completely from said portion and forms no connectingbridge with spout 12.

Once the plastic material filling the whole of mold cavity 31 sets,molds 30 a, 30 b, 30 c, 30 d are moved into the open configuration tofeed material 2 once more in direction A, extract the removable portion8, with respective opening device 3 formed on it, from molding unit 30,and insert another removable portion 8, on which to perform anothermolding operation, inside cavity 31.

The advantages of the method according to the present invention, and ofthe resulting packaging material, will be clear from the foregoingdescription.

In particular, the method described provides for obtaining an openingdevice 3 firmly connected to cover portion 10 of packaging material 2,but in which the cover portion is first pierced through and thenresealed by the plastic material forming spout 12 and pull ring 21. As aresult, package 1 has the necessary gas-sealing properties, while at thesame time being as easy to open as packages with no gas barrier. Thatis, to unseal the package produced using the method according to thepresent invention, the user simply has to tear the annular portion 19connecting the plastic parts, as opposed to the gas-barrier material,which has already been pierced through when injection molding openingdevice 3. More specifically, as shown in FIGS. 6 and 7, the gas-barriermaterial is removed completely from portion 19, and forms no connectingbridge with spout 12.

Moreover, cover portion 10 is pierced neatly, with no fraying, by thehigh pressure of the plastic material, thus greatly improving smoothpour-out of the food product.

Clearly, changes may be made to the method and resulting packagingmaterial as described herein without, however, departing from the scopeas defined in the accompanying Claims.

In particular, the method described may also be performed directly onblanks of packaging material, after they are formed into open containerson spindles, and before they are filled with the pourable food productand sealed.

The invention claimed is:
 1. A sealed package of pourable food productcomprising: a base layer of material that is folded and sealed, with athrough hole passing through the base layer of material so that an innerperiphery of the through hole surrounds a region entirely devoid of thematerial forming the base layer; at least one layer fixed relative tothe base layer and including a portion extending across the throughhole, the portion extending across the through hole possessing aninterior facing side which faces an interior of the sealed package, atleast a part of the portion of the at least one layer being surroundedby the inner periphery of the through hole; an opening device made ofplastic material, the opening device comprising an attachment portion, atubular spout and a pull member; the attachment portion being adhered tothe interior facing side of the portion of the at least one layerextending across the through hole; the tubular spout being integrallyinjection molded with the attachment portion and passing through the atleast one layer so that the tubular spout is positioned on a side of theportion of the at least one layer opposite the interior facing side andprojects away from the portion of the at least one layer; the pullmember being fixed relative to the attachment portion so that applying apulling force to the pull member also pulls the attachment portion anddetaches the attachment portion adhered to the interior facing side ofthe portion of the at least one layer, along an annular portion; and theattachment portion defining, with the at least one layer, auser-removable sealing portion of the spout that is removable by pullingthe pull member to unseal the package of pourable food product and allowthe pourable food product to be dispended from the package, theuser-removable sealing portion that is removed by pulling the pullmember being devoid of the material forming the base layer.
 2. Thesealed package as claimed in claim 1, wherein the pull member isintegrally injection molded with the attachment portion, and is spacedinwardly from the spout so that the tubular spout surrounds the pullmember.
 3. The sealed package as claimed in claim 1, wherein the atleast one layer including the portion extending across the through holeis a gas-barrier material.
 4. The sealed package as claimed in claim 3,further comprising a layer of heat-seal plastic material melted to theattachment portion of the opening device, the layer of heat-seal plasticmaterial overlying the gas-barrier material.
 5. The sealed package asclaimed in claim 1, wherein the spout includes a flange portionextending radially outwardly beyond an outer peripheral surface of thetubular spout, the flange portion being fixed to the base layer andbeing at least partially positioned on a side of the base layer facingtowards the interior of the sealed package.
 6. The sealed package asclaimed in claim 1, further comprising an external thread on an outerperipheral surface of the tubular spout, the external thread threadablyengaging an internal thread on a screw cap.
 7. The sealed package asclaimed in claim 1, wherein the attachment portion and the spout of aopening device are joined by an annular portion possessing across-section smaller than a cross-section of the attachment portion toform a tear line allowing detachment of the attachment portion from thespout when the pull member is pulled.
 8. A sealed package of pourablefood product comprising sheet material that is folded and sealed, thesheet material comprising at least a first layer made of a material anda second layer, the first layer including a through opening passingthrough the first layer, with a cover portion of the second layerextending across the through opening, the through opening in the firstlayer possessing an inner periphery surrounding a region entirely devoidof the material forming the first layer, the inner periphery of thethrough opening in the first layer surrounding at least a part of thecover portion of the second layer; the sheet material also comprising anopening device made of plastic material, injection molded onto the coverportion, and in turn comprising, integrally, an attachment portionadhering to a first side of the cover portion, and a spout extendingthrough a peripheral portion of the cover portion to project from asecond side, opposite the first side, of the cover portion; theattachment portion defining, with the cover portion, a user-removablesealing portion of the spout that is both removable by the user tounseal the package of pourable food product and allow the pourable foodproduct to be dispended from the package and entirely devoid of thematerial forming the first layer.
 9. The sealed package as claimed inclaim 8, wherein the second layer, including the cover portion of thesecond layer extending across the through opening, comprises gas-barriermaterial.
 10. The sealed package as claimed in claim 9, furthercomprising a third layer of heat-seal plastic material applied on afirst side of the second layer, the third layer being melted to theattachment portion of the opening device.
 11. The sealed package asclaimed in claim 8, wherein the opening device also comprises a pullring projecting integrally from the attachment portion through the coverportion of the second layer; the pull ring being pulled by the user toremove the sealing portion from the spout.
 12. The sealed package asclaimed in claim 8, wherein a part of the cover portion through whichpasses the plastic material of the opening device is sealed by theplastic material.
 13. The sealed package as claimed in claim 8, whereinthe spout has an external thread threadably engaging a correspondingthread of a screw cap.
 14. The sealed package as claimed in claim 8,wherein the attachment portion and the spout of the opening device arejoined by an annular portion possessing a cross-section smaller than across-section of the attachment portion, the annular portion defining atearable connection between the attachment portion and the spout.
 15. Asheet material for packaging pourable food product comprising at least afirst layer and a second layer, and having an opening passing throughthe first layer with a cover portion of the second layer extendingacross the opening, the first layer being made of a material and theopening possessing an inner periphery surrounding a region entirelydevoid of the material forming the first layer, at least a part of thecover portion being located in the region surrounded by the innerperiphery of the opening; the sheet material also comprising an openingdevice made of plastic material, injection molded onto the coverportion, and in turn comprising, integrally, an attachment portionadhering to a first side of the cover portion, and a spout extendingthrough a peripheral portion of the second layer to project from asecond side, opposite the first side, of the cover portion; theattachment portion defining, with the cover portion, a user-removablesealing portion of the spout that is removable by the user and that isentirely devoid of the material forming the first layer.
 16. The sheetmaterial as claimed in claim 15, wherein the second layer comprisesgas-barrier material.
 17. The sheet material as claimed in claim 16,further comprising a third layer of heat-seal plastic material appliedon a first side of the second layer, the third layer being melted to theattachment portion of the opening device.
 18. The sheet material asclaimed in claim 15, wherein the opening device also comprises a pullring projecting integrally from the attachment portion through the coverportion of the second layer; the pull ring being pulled by the user toremove the sealing portion from the spout.
 19. The sheet material asclaimed in claim 15, wherein a part of the cover portion through whichpasses the plastic material of the opening device is sealed by theplastic material.
 20. The sheet material as claimed in claim 15, whereinthe attachment portion and the spout of the opening device are joined byan annular portion possessing a cross-section smaller than across-section of the attachment portion, the annular portion defining atearable connection between the attachment portion and the spout.
 21. Asealed package of pourable food product comprising: a base layer ofmaterial that is folded and sealed, with a through hole passing throughthe base layer of material, the through hole including an innerperiphery and the entire area surrounded by the through hole beingdevoid of the material forming the base layer; at least one layer fixedrelative to the base layer and made of a material different from thebase layer, a portion of the at least one layer extending across thethrough hole in the base layer and possessing an interior facing sidewhich faces an interior of the sealed package, another portion of the atleast one layer overlying the base layer; an opening device made ofplastic material, the opening device comprising an attachment portion, atubular spout and a pull member; the attachment portion being adhered tothe interior facing side of the portion of the at least one layer; thetubular spout being integrally injection molded with the attachmentportion and passing through the at least one layer so that the tubularspout is positioned on a side of the portion of the at least one layeropposite the interior facing side and projects away from the at leastone layer; the pull member being fixed relative to the attachmentportion so that applying a pulling force to the pull member also pullsthe attachment portion; the attachment portion defining, with the atleast one layer, a user-removable sealing portion of the spout that isremovable by pulling the pull member and that is entirely devoid of thebase layer material; and wherein at least a part of the attachmentportion that is adhered to the interior facing side of the portion ofthe at least one layer is radially inward of the tubular spout.